There has been known a machine apparatus in which a rotational shaft of a rotary machine is coupled to a drive shaft of a prime mover through a coupling (or a shaft coupling) and the drive shaft is rotated to thereby rotate the rotational shaft. One example of such a machine apparatus is a pump apparatus. The pump apparatus includes a motor which is a prime mover, and a pump which is a rotary machine. A drive shaft of the motor is coupled to a rotational shaft of the pump by the coupling. In the pump apparatus, a torque of the drive shaft of the motor is transmitted to the rotational shaft of the pump through the coupling, thereby rotating an impeller which is fixed to the rotational shaft.
Usually, a coupling guard, which covers the coupling and a vicinity of the coupling, is provided so that a human being does not touch the coupling, an exposed portion of the rotational shaft of the pump, and an exposed portion of the drive shaft of the motor when they are rotating at a high speed.
The coupling guard is installed in the pump apparatus when an operation of the pump apparatus is stopped and the drive shaft of the motor and the rotational shaft of the pump are coupled to each other. Removal of the coupling guard is also conducted when the drive shaft of the motor and the rotational shaft of the pump are coupled to each other. However, it takes a lot of time to install and remove the coupling guard when the drive shaft of the motor is coupled to the rotational shaft of the pump, because the coupling guard is made up of many parts. This problem can occur not only in the pump apparatus, but also in all machinery which uses a coupling through which a rotational shaft of a rotary machine is coupled to a drive shaft of a prime mover.